(1) Field of the Invention
The present invention relates to a compressor for an air-conditioning system used in a vehicle such as an automobile, and more particularly, to a multi-piston swash plate type compressor with an internal lubricating arrangement for lubricating internal movable parts therein.
(2) Description of the Related Art
U.S. Pat. No. 4,403,921 discloses a multi-piston swash plate type compressor having such an internal lubricating arrangement, comprising: a cylinder block body assembled from a pair of cylinder block halves to form a swash plate chamber therebetween, the cylinder block halves having a same number of cylinder bores which are concentrically formed with respect to the central axis of the cylinder block body, the cylinder bores of one cylinder block half being aligned and registered with the cylinder bores of the other cylinder block half, respectively, with the swash plate chamber intervening therebetween; common piston members slidably received in the pairs of aligned cylinder bores, respectively; a swash plate member disposed within the swash plate chamber to be slidably engaged with the common piston members so that the pistons are reciprocated in the pairs of aligned cylinder bores, respectively, by rotation of the swash plate member; a shaft member which extends into an axial bore of the cylinder block body so that it passes through the swash plate chamber and on which the swash plate member is fixedly mounted; a pair of radial bearings provided within the axial bore sections in the cylinder block halves, respectively, for rotatably supporting the shaft member in the axial bore of the cylinder block body; a pair of thrust bearings provided around the shaft member at the sides of the swash plate member; a pair of dish-like housing members mounted on the end faces of the cylinder block body, respectively, so as to form a suction chamber and a discharge chamber between each of the dish-like housing members and the corresponding end face of the cylinder block body; and a disc-like reed valve assembly disposed between each of the dish-like housing members and the corresponding end face of the cylinder block body so that each of the cylinder bores is communicated with the corresponding suction and discharge chambers through the intermediary of the corresponding suction and discharge reed valve elements of the disc-like reed valve assembly.
In the compressor as mentioned above, the cylinder block halves, the dish-like housing members, and the disc-like reed valve assemblies are assembled as a unit by elongated screws extended into screw bores formed in these compressor components in the vicinity of the periphery thereof, the screw bores being in communication with the swash plate chamber and the suction chambers. The swash plate chamber is adapted to be fed with a refrigerant including a lubricating oil from an evaporator of an air conditioning system. The refrigerant including a lubricating oil is then fed from the swash plate chamber to the suction chambers through the screw bores.
In this conventional arrangement, it is intended that the movable parts are lubricated by the lubricating oil included in the refrigerant by introducing it into the swash plate chamber. In particular, since there are sliding surfaces between the swash plate member and the piston members within the swash plate chamber, they are lubricated by introducing the refrigerant including a lubricating oil into the swash plate chamber. Also, the thrust bearings are disposed within the swash plate chamber at the sides of the swash plate member so that they too are lubricated by the lubricating oil included in the refrigerant. Furthermore, since the axial bore sections of the cylinder block halves in which the radial bearings are disposed are in communication with the swash plate chamber, the refrigerant including a lubricating oil can obtain access to the radial bearings for lubrication thereof.
However, with the conventional internal lubricating arrangement as mentioned, a large part of the refrigerant including a lubricating oil introduced to the swash plate chamber is directly fed to the suction chambers through the screw bores of the cylinder block halves without sufficient circulation of the refrigerant within the swash plate chamber, so that it is impossible to obtain sufficient lubrication of the movable parts of the compressor. For this reason, during a high speed run of the compressor, a seizure of the movable parts may occur.
U.S. Pat. No. 4,381,178 also discloses a multi-piston swash plate type compressor wherein the internal lubricating arrangement is improved in comparison to that of the above-mentioned U.S. Pat. No. '921. According to this internal lubricating arrangement, not only is the refrigerant including a lubricating oil fed from the swash plate chamber to the suction chamber, but also the axial bore sections in the cylinder block halves are in communication with the suction chamber so that a part of the refrigerant from the swash plate chamber is fed thereto. In other words, it is intended that the refrigerant including a lubricating oil flows through clearances among the component elements of the thrust and radial bearings by communicating the swash plate chamber with the suction chambers, so that an effective lubrication of the thrust and radial bearings can be achieved. However, U.S. Pat. No. 4,381,178 fails to carry out an effective lubrication of the thrust and radial bearings because a large part of the refrigerant has a tendency to flow from the swash plate chamber to the suction chambers through the screw bores because of the high flow resistance of the axial bore sections in the cylinder block halves. In short, although this internal lubricating arrangement is an improvement in comparison to that of the first-mentioned US patent, a seizure at the movable parts of the compressor still may occur during a high speed run thereof.